How to combine two rigs?
If the armatures have the same bone names:

Remove the armor from its rig (select the object and press Alt+P or remove the relationship in Properties &gt; Modifiers)
Parent it to the character rig (select the armor object, select the character armature and press Ctrl+P &gt; Armature Deform).

If the armatures have different bone names:

Remove the armor from its rig (select the object and press Alt+P or remove the relationship in Properties &gt; Modifiers)
Parent it to the character rig (select the armor object, select the character armature and press Ctrl+P &gt; 'Armature Deform With Empty Groups'.
Select the armor object, switch to Edit mode in the 3D view and go to Properties &gt; Object Data Properties &gt; Vertex Groups.
Make sure no vertices are selected in the 3D viewport by pressing Alt+A
In Properties &gt; Object Data Properties &gt; Vertex Groups you should see all of the names of the bones of the armor armature (even though it is no longer linked). Click a name, click 'Select' to select all the vertices in that group, click the name of the character armature group you want to that piece of armor to follow then click assign.
Test in 3D Viewport &gt; Pose mode to see if it is working as intended.
Repeat steps 4-6 for all the bits of armor.